Based on kbsingh's article, upgrade a machine to CentOS5 in place. I am using an x86_64 machine as well.
Gave up on this, when I couldn't get the machine to boot with the options.
References
![[WWW]](/wiki/rightsidebarsmaller/img/moin-www.png)
http://www.karan.org/blog/index.php/2005/06/15/upgrading_to_centos4_over_a_remote_vnc_c - http://www.centos.org/docs/5/html/Installation_Guide-en-US/s1-kickstart2-options.html
Grub kernel line x86_64: (untested)
kernel /boot/vmlinuz vnc vncpassword=SOMEPASSWORD ip=192.168.1.105 netmask=255.255.255.0 gateway=192.168.1.2 dns=192.168.1.2 hostname=centos5.example.com headless ksdevice=eth0 method=http://mirror.centos.org/centos/5/os/x86_64/ lang=en_US keymap=us
Grub kernel line i386: (untested)
kernel /boot/vmlinuz vnc vncpassword=SOMEPASSWORD ip=192.168.1.105 netmask=255.255.255.0 gateway=192.168.1.2 dns=192.168.1.2 hostname=centos5.example.com headless ksdevice=eth0 method=http://mirror.centos.org/centos/5/os/i386/ lang=en_US keymap=us
My favorite mirror is a more local one though:
http://centos.arcticnetwork.ca/5/os/